I was really excited to use a Domsjo double bowl “farmhouse” style kitchen sink in our new kitchen. Although it comes with one hole pre-drilled in the center for a faucet, the California Plumbing Code requires an air gap to be installed. The purpose of these devices to to make sure water will not back flow from your sink into your dishwasher if your sink clogs up. Personally, I don’t like the look of them, and they are not required by code in many states (or apparently in Europe, based on the sink’s design). I have read about exceptions being granted by some building inspectors, or in some jurisdictions. However, this was not the case for me, and my inspector would not budge.
So it was up to me to drill a hole in my new sink, to allow the installation of the air gap. I am a reasonably handy person but not an expert by any means.
Sponge and water
Small piece of plywood
Hole Saw – This is a special drill bit called a “hole saw” that can drill a 1-3/8” hole. This is a standard size for an air gap. I ordered a set from Amazon for $24.
These are the bits I used, but many are available:
Precision Diamond Tools 5 Diamond Dust Hole Saw for Tile / Glass/ Marble / Granite / Ceramic / Porcelain / Stone Holesaw 3/4″, 1″, 1-3/16″, 1-3/8″, 1-5/8″ Electroplated Diamond Drill Bits
Step 1 – Measure where you want the hole to be. For me, this involved drawing a circle on the bumpy part of the sink with a dry erase marker.
Step 2 – Make a wooden guide with a hole, which will hold the hole saw in place. I had read that the hole saw blade would have a tendency to “walk” across the sink, and not stay put in one place at the beginning of the drilling. So I got a small piece of plywood, about a foot square, and cut a 1 3/8” hole in it.
Step 3 – I put the diamond hole saw bit into my electric drill, and first practiced cutting a hole through an old piece of ceramic tile. It took about 60 seconds. I used a wet sponge to drizzle water on the cutting area, to help keep the saw cool and remove the tile dust. I didn’t notice the hole saw “walking” at all, but decided to use a plywood guide on my sink anyway.
Step 4 – I put the plywood on the sink, and lined up the hole with the circle I had drawn on the surface of the sink. Then, with a friend holding the plywood firmly in place, I put the hole saw into the the plywood hole, which acts like a guide and keep the hole saw in place. I used the drill at a fairly low speed, and it cut through the sink almost like butter. It cuts with a grinding process, so there was no cracking or chiping. Every minute or so I would stop drilling and drizzle water on the area to wash out the dust. In less than 10 minutes I had a hole in my sink, right where I wanted it.